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Avalanche Forecast

Archived

Mar 10th, 2023–Mar 11th, 2023

Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.
Alpine
Natural avalanches unlikely, human triggered possible.
Treeline
Natural avalanches unlikely, human triggered possible.
Below Treeline
Natural avalanches unlikely.

Regions

South Rockies, St. Mary, Bull, Elkford East, Elkford West.

Diligently maintain a conservative mindset. You may not see signs of instability on the surface however the deep persistent weak layer remains a major concern at the bottom of the snowpack.

Avoid shallow, rocky, and wind-loaded terrain where triggering slab avalanches is most likely.

Confidence

Moderate

Avalanche Summary

No recent avalanches have been reported in this region.

On Tuesday, a deep persistent slab avalanche was triggered by a cornice or solar input in extreme, rocky terrain in the Elkford area. See the MIN for a photo.

Snowpack Summary

Up to 15 cm of low-density new snow has accumulated over 40-50 cm of wind-affected snow in the alpine and open treeline. On solar slopes, they overlie a thin sun crust.

In the Purcells, several weak layers from Jan and Feb can be found down 50 to 120 cm however they are showing signs of strengthening. The mid-snowpack is generally well-settled.

The lower snowpack is made up of a widespread layer of large, weak basal facets and depth hoar in some areas. this weakness has been responsible for a number of recent very large, destructive avalanches and will continue to be a concern.

Weather Summary

Friday night

Mainly cloudy with isolated flurries, up to 5 cm of accumulation. Alpine temperatures drop to a low of -13 °C. Ridge wind light from the northeast. Freezing level at valley bottom.

Saturday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -7 °C. Light ridge wind from the southwest. Freezing level rises to 900 meters.

Sunday

A mix of sun and cloud with isolated flurries. Alpine temperatures reach a high of -5 °C. Ridge wind 15 gusting to 40 km/h from the southwest. Freezing level rises to 1200 meters.

Monday

Cloudy with mixed precipitation 5-15 cm of new snow accumulation at upper elevations. Alpine temperatures reach a high of 0 °C. Ridge wind 20 to 55 km/h from the southwest. Freezing level rises to 2000 meters.

More details can be found in the Mountain Weather Forecast.

Terrain and Travel Advice

  • Avoid steep, rocky, and wind effected areas where triggering slabs is more likely.
  • Use conservative route selection and resist venturing out into complex terrain.
  • Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
  • Wind slabs may be poorly bonded to the underlying crust.

Problems

Deep Persistent Slabs

Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.